Field of the Invention
The present invention relates to a medical device used to remove gas and liquid from the plural cavity between the lung and the chest wall. It is useful in treating a variety of related conditions including pneumothorax (collapsed lung), tension pneumothorax (collapsed lung pressing on the heart), and pneumohemothorax (collapsed lung with air and bodily fluids in the pleural cavity).
Discussion of Current Methods
A pneumothorax, tension pneumothorax, or pneumohemothorax is caused by the progressive build-up of air within the pleural space or pleural cavity between the chest wall and the lung and is often a result of a laceration to the lung, which allows air and/or bodily fluids to escape from the lung into the pleural cavity.
In mammals, inhalation causes the chest walls to move up and out and the diaphragm, at the lower portion of the thorax, to depress. The lungs, pushed by atmospheric pressure, expand with air to match the pressure gradient. On exhalation, the chest walls move down and in and the diaphragm rises, squeezing the lungs, forcing air from them through the nose and mouth except in the case of a laceration of the lung. The lungs remain inflated, under normal conditions, because of the slight negative pressure in the plural cavity. However, chest trauma allowing air and/or bodily fluids into the pleural space can raise the pressure of the environment, and subsequently collapse the lung.
During respiration, a build up of air and pressure can occur in the pleural space allowing the collapsed lung to push against the pleural wall and may obstruct venous return of deoxygenated blood to the heart. The eventual result of this obstruction from the tension pneumothorax, or pneumohemothorax may result in decreased heart function or traumatic arrest.
Problems with the cannula inserted by the needle are the difficulty in applying sufficient pressure to force the needle with the external cannula into and through the chest wall. When pressure is applied, even a skilled operator may inadvertently puncture the lung with the needle upon entry into the pleural cavity. This would further compound the build-up of air or fluid into the pleural cavity, nullifying the benefits of the application. Further problems can be created after removal of the insertion needle if the cannula is kinked or twisted so as to restrict the passage through the cannula. Also, the open cannula can easily convey non-sterile air into the pleural cavity.
It is desirable to provide a medical device which mitigates the problems associated with the current methods including those involving a plastic cannula. These problems include ease of insertion, inadvertent entry or laceration of the lung during insertion, prevention of any obstruction of the airway and prevention of non-sterile air entering the pleural cavity.